The present invention relates to a solid propellant gas generator impulse management scheme for high mass flow turn-down ratio. More particularly, the present invention is directed to a solid divert and attitude control system that has particular utility on kinetic hit-to-kill weapons and other types of missiles.
Divert and attitude control systems (DACS) are required for maneuvering kinetic hit-to-kill weapons. Kinetic kill vehicles (kv) or missiles are used to destroy missiles or other airborne or spaceborne objects such as satellites. Impulse flexibility (energy management) is a critical performance parameter for these systems because greater flexibility means a more capable vehicle. Liquid propulsion systems currently provide the most flexibility because they possess inherent impulse management through on-off operation; that is, propellant is only used when needed. However, the current generation of liquid systems is toxic and presents safety and environmental hazards. Hybrid propulsion systems, like liquid systems, are flexible in energy management and can be made non-toxic for improved safety; however, density-impulse is greatly reduced. Solid propulsion systems on the other hand have the highest density-impulse and can be made to meet all safety and insensitive munitions requirements, but do not have the desired energy management flexibility.
Various methods have been attempted to provide increased energy management capability to solid divert and attitude control systems such as: pulsed operation from independently ignitable grains, dP/dT extinguishments and re-ignition with multiple igniters, and pressure control through exit area modulation either proportionally or by pulse width modulation (PWM). Each of these methods has limitations in operation (for instance, limited impulse flexibility and low turn down ratio) and other undesirable attributes (for example, increased components, complexity, cost, and weight).
The management scheme and system of the present invention overcomes these drawbacks.
It is an object of the present invention to provide a solid divert and attitude control system that can achieve a turn-down ratio in excess of thirty to one.
It is a further object of the present invention to provide a solid divert and attitude control system as above that has a thrust response (rate of change of thrust) which exceeds that of a hypergolic system.
The foregoing objects are attained by the solid divert and attitude control system of the present invention.
In accordance with the present invention, the solid divert and attitude control system comprises a solid propellant gas generator having a solid propellant grain with a profile for generating different thrust levels during different portions of a flight, a control valve means for modulating the effective exit area of the solid propellant gas generator, and a controller for calculating the propellant burn rate and for controlling the operation of the control valve means to alter the pressure being generated by the solid propellant gas generator during a coast phase of the vehicle""s flight. In a preferred embodiment of the present invention, the solid propellant generator grain profile includes a first high thrust or boost phase grain, an intermediate low thrust or sustain phase grain, and a second high thrust or boost phase grain along the web.
The solid divert and attitude control system of the present invention has a number of advantages including a turndown ratio in excess of 30:1. Further, the system enables a wide variety of mission timelines to be accommodated due to the operation of the controller. Still further, the system of the present invention has a moderate thrust midcourse correction capability of 40% to 50% of boost phase thrust depending on the turndown ratio and enables a solid propulsion system to have nearly the same impulse flexibility as a liquid propulsion system.
Other details of the solid divert and attitude control system of the present invention, as well as other objects and advantages attendant thereto, are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.